Flexible Joint Sealants for Concrete, Floors & Construction

The gap may look simple. What happens inside it isn't. Concrete expands, floor joints take traffic, façades move with temperature changes & connections between different building materials can pull in different directions. Soudal Polyurethane Sealant gives builders, concreters, flooring contractors, maintenance crews & construction professionals elastic joint-sealing options matched to those different conditions.

The Soudaflex range covers PU sealants for concrete joints, expansion joints, floors, façades, window & door connections plus suitable construction bonding. Rather than treating every polyurethane cartridge as interchangeable, compare how the joint moves, whether it is horizontal or vertical, what the substrate is & what the finished joint will encounter.

Working on concrete joints or surrounding repairs? Browse Concrete Repair & Restoration. For exterior joints exposed to rain, temperature changes & Australian weather, explore Weatherproofing Supplies.

Within the Soudaflex range, the product code matters. 20LM targets high-movement joints, 33SL brings self-levelling performance, 36FL is built around floor joints while 42FX & 45FC PRO extend into flexible sealing & bonding. Choosing from those differences is far more useful than selecting a polyurethane sealant simply because it fits the gap.

What Are Soudal Polyurethane Sealants?

Soudal polyurethane sealants are elastic joint-sealing products used across demanding building, concrete, flooring & construction applications.

Soudaflex polyurethane products are one-component formulations that cure through atmospheric moisture. Once cured, they remain elastic, allowing suitable joints to accommodate movement rather than being filled with a rigid material.

Depending on the exact Soudaflex product, uses can include:

► Concrete expansion joints
► High-movement building joints
► Floor & shrinkage joints
► Horizontal construction joints
► Window & door perimeter connections
► Façade joints
► Connections between different construction materials
► Suitable joints exposed to oils, fuels or lubricants
► Roof-tile bonding
► Flexible construction bonding
► Vibrating constructions

A polyurethane joint sealant should therefore be selected around the joint's actual working conditions rather than polyurethane chemistry alone.

Why Choose Soudal Polyurethane Sealant?

Movement Is Part of the Joint

Expansion, contraction, vibration & changes between adjoining materials can repeatedly place a sealant under stress.

A correctly selected elastic PU sealant can accommodate that movement while maintaining adhesion to properly prepared joint faces.

Where movement is substantial, modulus becomes especially relevant. Lower-modulus sealants stretch with less force, helping reduce stress transferred into the edges of suitable high-movement joints.

Concrete Needs the Right Type of Flexibility

Concrete joints aren't all doing the same job.

An expansion joint may need substantial movement accommodation while a floor joint may have different exposure, orientation & traffic considerations. Soudal separates these requirements across products such as Soudaflex 20LM, 33SL & 36FL.

That makes product selection more precise than relying on one general-purpose cartridge for every concrete joint.

Floor Joints Bring Their Own Demands

Workshops, warehouses & construction floors can expose joints to traffic, equipment, cleaning processes & occasional chemical contact.

Soudaflex 33SL & 36FL are particularly relevant when floor-joint performance is the priority.

Sealing & Bonding Can Overlap

Some applications require elastic sealing while others also need adhesion between components.

Soudaflex 42FX & 45FC PRO combine polyurethane sealing with suitable flexible bonding capabilities, expanding their use across general construction work.

Exterior Joints Need Exposure Considered

Weather-facing joints encounter sunlight, temperature changes & moisture over their service life.

Selected Soudaflex products provide strong weather & UV resistance for suitable exterior construction applications.

For crews preparing tools & equipment ahead of changing site conditions, Spring Jobsite Prep Getting Your Gear Ready provides practical jobsite preparation guidance.

Common Applications

Concrete Expansion Joints

Expansion joints are created because movement is expected.

Joint width, depth, surrounding material, expected movement & joint-face preparation all influence the sealant required. Soudaflex 20LM is particularly relevant where high movement & low-modulus behaviour are priorities.

Workshop & Warehouse Floors

Floor joints may experience traffic, machinery, cleaning & contact with oils or other workshop fluids.

Soudaflex 33SL & 36FL are the products to compare when the job centres on horizontal floor joints.

For wider floor preparation, installation & maintenance requirements, browse Flooring Tools & Adhesives.

Window & Door Connections

Frames & surrounding construction materials can expand or contract at different rates.

Soudaflex 20LM & 45FC PRO can be relevant to suitable frame-to-wall connection joints depending on substrate, movement, joint design & exposure.

If cavities around frames also require filling or insulation, Soudal PU Foam covers dedicated expanding & flexible foam products.

Façades & Exterior Connections

Temperature cycles, weather & building movement repeatedly load exterior joints.

A suitable elastic construction sealant helps accommodate that movement without turning the connection into a rigid fill point.

Roof-Tile Bonding

Soudaflex 42FX & 45FC PRO extend beyond conventional joint sealing.

Both are specified for suitable roof-tile bonding applications where flexible adhesion is required.

For surrounding roofing requirements, browse Roofing Materials & Sealants.

Vibrating Constructions

Not every movement joint changes slowly.

Mechanical vibration creates repeated stresses through bonded components. Soudaflex 42FX & 45FC PRO can be used for suitable structural bonding applications involving vibrating constructions.

Product Selection Guide

Soudaflex 20LM – For High-Movement Joints

Movement is the clue in the name: LM means low modulus.

Soudaflex 20LM is a permanently elastic polyurethane construction sealant developed particularly for concrete & high-movement building joints.

Typical applications include:

► Concrete expansion joints
► High-movement construction joints
► Connection joints
► Window & door frame-to-wall joints
► Joints between different construction materials

Soudaflex 20LM conforms to ISO 11600 F 25 LM. Its technical information specifies approximately ±25% maximum allowed distortion plus elongation at break above 800% under stated test conditions.

For a joint expected to move substantially, 20LM is the logical Soudaflex product to compare first.

Soudaflex 33SL – For Self-Levelling Horizontal Joints

Need the fresh sealant to settle across a horizontal joint?

Soudaflex 33SL is a one-component self-levelling polyurethane sealant intended for suitable horizontal applications.

Typical uses include:

► Floor joints
► Horizontal building joints
► Connection joints
► Expansion & dilatation joints
► Suitable joints exposed to hydraulic fluids, lubricants, oils or fuels

Its flow characteristics help produce an even surface across suitable horizontal joints. Soudal specifies a maximum slope of approximately 3%, making orientation an important part of selection.

For fuel & oil exposure, Soudal distinguishes normal splash or spillage from more intense contact. Up to one week of intense contact or immersion is specified when used with Primer 100 under the stated conditions.

Soudaflex 36FL – For Dedicated Floor Joint Sealing

If the application begins with the words floor joint, Soudaflex 36FL deserves attention.

It is an elastic one-component polyurethane floor-joint sealant for applications including:

► Concrete floor shrinkage joints
► General flooring joints
► Horizontal construction joints
► Expansion & dilatation joints
► Suitable joints exposed to hydraulic fluids, lubricants, oils or fuels

Soudal specifies resistance to splash & spillage contact with oils & fuels. More intense contact or immersion for up to one week requires the specified Primer 100 system under the relevant conditions.

Soudaflex 42FX – For Sealing Plus Flexible Bonding

Some jobs cross the line between filling a joint & bonding components.

Soudaflex 42FX is an elastic one-component polyurethane sealant & adhesive suited to general construction sealing plus appropriate flexible bonding work.

Applications include:

► General building sealing & bonding
► Shrinkage joints in concrete floors
► Façade-element joints
► Structural bonding in vibrating constructions
► Roof-tile bonding

Its permanently elastic cured state plus adhesion, weather resistance & UV resistance make it relevant where both sealing & bonding performance are required.

Soudaflex 45FC PRO – For Versatile Construction Work

Soudaflex 45FC PRO is another elastic polyurethane construction sealant & adhesive, with applications spanning joint sealing & flexible bonding.

Typical uses include:

► General building sealing & bonding
► Window & door frame connections
► Interior & exterior floor joints
► Expansion joints between different construction materials
► Roof-tile bonding
► Structural bonding in vibrating constructions

Its properties include permanent elasticity, bubble-free curing, strong adhesion plus resistance to UV exposure & various chemicals.

When choosing between 42FX & 45FC PRO, compare the exact substrates, movement, exposure & application requirements rather than selecting by one specification alone.

Match the Sealant to the Problem

High Movement?

Start with 20LM.

Its low-modulus characteristics make it particularly relevant to expansion joints & other construction joints where substantial movement is expected.

Horizontal Joint That Needs to Self-Level?

Look at 33SL.

Its flowing consistency is specifically useful across suitable horizontal applications within the stated slope limit.

Dedicated Floor Joint?

Compare 33SL & 36FL.

Choose between self-levelling behaviour & the requirements of the particular floor-joint application.

Need Flexible Bonding Too?

Compare 42FX & 45FC PRO.

Both extend beyond conventional joint filling into suitable elastic bonding work.

Oils or Fuels Around the Joint?

Pay particular attention to 33SL & 36FL plus the exact exposure conditions.

Occasional splash or spillage is different from prolonged or intense chemical contact.

Permanent Water Exposure?

Treat that as a different application.

Standard polyurethane construction sealants aren't intended for continuous water immersion. Permanently submerged joints, water pressure & specialised wet structures require products specifically suitable for those conditions.

For surrounding moisture-control systems, browse Waterproofing & Damp Proofing.

Getting a Polyurethane Joint Right

Start With Movement, Not Cartridge Size

A wide gap isn't automatically a high-movement joint.

Consider what the adjoining materials are, how much movement is expected & what the joint was designed to do. Those questions help determine the required sealant behaviour.

Check Whether the Joint Is Horizontal or Vertical

Orientation changes application behaviour.

A self-levelling sealant such as 33SL is useful because it flows. That also means its slope limitations need to be respected.

Prepare the Joint Faces Properly

Dust, loose material, grease & contamination can compromise adhesion before movement performance even becomes relevant.

Joint faces should be sound, clean & appropriately prepared before sealant application.

Depending on substrate & service conditions, Primer 100 or another specified primer may be required.

Control the Depth of the Sealant

More sealant isn't automatically better.

Correct joint geometry helps an elastic sealant move as intended. Suitable backing material can control depth & help establish an appropriate joint profile.

Accurate dimensions also matter before application. Browse Measuring & Layout Tools for equipment suited to checking dimensions & site layout.

Tool the Joint While It's Workable

Tooling isn't simply cosmetic.

It helps fresh sealant make good contact with prepared joint faces while establishing the required exposed profile before skin formation progresses.

Expert Tips

Don't Judge a Sealant by Hardness Alone

A firmer sealant isn't automatically a better sealant.

High-movement joints often benefit from lower-modulus behaviour because the sealant can deform while transferring less stress into the joint edges.

Don't Treat 33SL as a Vertical Sealant

The characteristic that makes 33SL useful—its ability to self-level—also defines where it belongs.

Check joint slope before opening the cartridge.

Treat Chemical Exposure as a Spectrum

A splash of workshop fluid isn't the same as prolonged immersion.

When selecting 33SL or 36FL around fuels, oils, lubricants or hydraulic fluids, consider the expected duration & intensity of contact plus the specified primer requirements.

Backing Material Does More Than Save Sealant

A suitable backing rod helps control sealant depth & can prevent unwanted three-sided adhesion.

That gives an elastic joint a more suitable profile for movement.

Clean Preparation Tools Before Residue Becomes the Next Problem

Joint preparation can leave tools exposed to dust, old sealant & site grime. How To Clean Your Gear Without Ruining It covers practical equipment-cleaning considerations.

Protect Hands Around Preparation & Application

Surface preparation, primers & fresh construction sealants require appropriate handling.

Browse Hand & Arm Protection for suitable trade protection.

Check Paint Compatibility Before Finishing

Selected polyurethane sealants can be painted after curing, but coating systems can behave differently.

Test compatibility with the intended paint or coating where required rather than assuming every combination will perform identically.

Read the Information for the Exact Soudaflex Product

20LM, 33SL, 36FL, 42FX & 45FC PRO belong to the same broad polyurethane family but aren't interchangeable.

Follow the current product label, Technical Data Sheet & Safety Data Sheet for the exact cartridge being used. How to Read a Safety Data Sheet - A Quick Guide for Workshop Operators can help crews work through supplied safety information.